Electrical system



y 1944- M. A. EDWARDS ELECTRICAL SYSTEM Filed Oct. 17,

Fig.2.

SPEED TACK Inventor" Martin Afidwards,

torney.

Patented July 4, 1944 UNITED STATES PATENT OFFICE ELECTRICAL SYSTEMMartin A. Edwards, Scotia, N. Y assignor to General Electric Company, acorporation oi New York Application October l'l, 1942, Serial No.462,393

18 Claims.

vide an improved electrical system for the control of prime movertesting generators such as dynamometers.

Further objects and advantages 01' my invention will become apparent andmy invention will be better understood from the following descriptionrelerringto the accomp y drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming part oi this specification.

In the drawing, Fig. 1 schematically iilustrates an electrical systemembodying my invention for the control oi a dynamometer used in testingan internal combustion engine; Fig. 2 illustrates the characteristics ofthe auxili exciter shown in Fig. 1: Fig. 3 schematics y illustratesanother electrical system embodying my invention; and Fig. 4schematically illustrates a Iurther embodiment of my invention appliedto an engine testing system.

Referring to the drawing, I have shown a prime mover it, such as aninternal combustion engine, arranged to drive the rotatable member II ata main-dynamo-electric machine, such as an inductor type eddy currentgenerator, arranged as a dynamometer for testing the engine. Therotatable member II is adapted to be driven by the primemover I I by ashaft i2 and is also connected by a suitable connection, such as a shaftit, to the rotatable member or armature l4 oi an auxiliary directcurrent exciter generator. This exciter armature II is provided with awinding connected to a commutator l! with which brushes II and i1 forman electrical contact. Excitation is provided to the armature N by afield exciting winding ll which is energized from a suitable source ofelectrical power supply I! and is adapted to be controlled by a variableresistance 20. The excitation provided by the field exciting winding itto the exciter is such that the machine normally would operate as amagnetically unsaturated machine. and the terminal voltage across thebrushes It and ll of the armature II would be substantially proportionalto the speed the armature it due to the excitation provided by thiswinding, as represented by curve II in Fig. 3. For testing certain typesat prime movers, it is desirable that the excitation provided by thisauxiliary exciter should not have a linear characteristic, asrepresented by the curve 2!, but would bear some other non-linearcharacteristic relative to the speed 0! the prime mover. In order toobtain such a characteristic, 9. held exciting winding 22 is arranged toprovide a component of excitation to the auxiliary exciter which iscumulative to the excitation provided by the field exciting winding II.This field exciting winding 22 is connected in shunt across the brushesI! and ll of the auxiliary exciter through a variable resistance 23. Theenergization oi the iield exciting winding 22, therefore, is responsiveto the speed of the auxiliary exciter armature II, and the voltageinduced by the excitation of the fleld exciting winding 22, therefore,varies substantially as the square 0! the speed oi. the auxiliaryexciter armature It, as represented by the curve 24 in Fig. 2. Theresultant voltage 01' the auxiliary exciter may be represented by thecurve 25 in Fig. 2. This voltage speed characteristic of the auxiliaryexciter can be varied by varying the resistances 20 and 23 to providevarious iorms of excitation dependent upon any predetermined desiredcharacteristic of the main dynamometer.

The auxiliary exciter of the type shown in this figure may not besuiiiciently sensitive and may have too slow a speed of response toprovide the desired control for the main dynamometer. In order toincrease these two equalities oi the system, the main generator isprovided with a field exciting winding 26 which is arranged to beenergized by a main exciter 21 of the armature reaction excited type.This main exciter 21 is provided with a rotatable member or armature 2!having a winding connected to a commutator and is provided with a set ofprimary brushes 2! and SI electrically connected together externally ofthe armature circuit by a short-circuiting conductor ii to complete aprimary circuit through the armature 28. A set of secondary brushes 82and SI is electrically displaced irom the primary brushes 2! and 30about the commutator oi the armature 18 to provide a secondary circuitthrough the armature. These brushes 3! and II are connected to thedynamometer field exciting windingli through a compensating fieldexciting winding II and a potentiometer or series resistance 15. Themain component of excitation is provided to the main exciter 21 by afield exciting winding I! which is connected to the brushes ii and i1 01the auxiliary exciter armature ll. The energizing voltage of thiscontrol ileld exciting winding SI, therefore, may be non-linearlyresponsive to the speed of the dynamometer and the prime mover and maybe varied to produce the desired dynamorneter operating characteristic'This control field exciting winding is adapted to provide a component ofexcitation along the secondary brush commutating axis of the mainexciter 21, as indicated by the arrow 31, which will induce a voltagebetween the exciter primary brushes 1! and I0 and produce a primaryshort-circuit current through the primary circuit oi' the armature It.This short-circuit current will produce a primary armature reaction. asindicated by the arrow II, which in turn will be cut by the conductorsof the winding on the armature II and will induce a voltage between thesecondary brushes I2 and II which will energize the dynamometer ileldexciting winding II. when the current flows through the secondarycircuit oi the armature II, a secondary component of armature reactionwill be produced. as indicated by the arrow 8|, which is opposed to thecontrol component of excitation 31. In order to minimize the componentof excitation required oi the control ileld exciting winding 30, thecompensating ileld exciting winding 31 is constructed and arranged toprovide a component of excitation. as indicated by the arrow Iii,substantially equal and opposite to the component of armature reactiondue the flow of current through the secondary armature circult. Thespeed oi response of the main exciter ll is iurther increased byarrangin a field exciting winding ll adapted to provide a component ofexcitation cumulative to the excitation ll of the control ileld excitingwinding It, as indicated by the arrow 12, also along the secondary brush'commutating axis. This winding ll is connected acrossthe resistance IIand the energizing voltage 0! the control field exciting winding suchthat this ileld exciting winding normally is deenergised; This isobtsinedbymahingtheresistancellsuchthst the voltage drop thereacross' issubstantially equal to the voltage across the control neld ex citingwinding I. and the iield exciting windingllisconnectedacmsstheseyoltegesinoppm sition to each other so thatsubstantisllyno voltage normally exists winding'll. However. when achsns tahesplsceintheenergbdng'voltsgeoithsileldercitingwindingitschangewilloccurinthe.current flowing through the secondary brushes and consequently throughthe resistance II.v'lheresistancellismsdesuohthstthevoltsgedroptberescrossduetothechlnseinsecondsrycurrent therethrmigh is substantially lessthsnthecbsngeintbevoitasejmpressed scrossthe ileld exciting winding uspch thatsncurrentflows'throughtheileld exciting winding 4| sndprovldess componentoi energisaton l2 slongthesecondsrybrnshcommmtstingaxisoltheenclterttemulstiveororposedtothsoomponentiloremcitatlmoitheneidexcitinswindingllii'tnesnergishgvoltaeeoithewindinglirlsesortalhrespectlvely.Thiscsusesarurtherehsngeinthesecondary current'ot the-exciter TI whichresults in s. turthercorrospondimemngeinthevoltsgedrop across theileldexciting assaeao across the resistance 1! until the dropacross t isresistance is substantially equal and opposite to the voltage across thefield exciting winding 86. When this occurs. the field exciting windingll again is deenergized. Thus. the ileld exciting winding H is energizedonly when the current in the exciter secondary brushes is other than apredetermined value relative to the energizin voltage oi the controlfield exciting winding 3| and thereby maintains a predeterminedrelationship therebetween between the cnergisation or the dynamometerfield exciting winding 2| and the energization of the exciter controlfield exciting winding 38 and produces a more rapid change in theenergizing current of the dynamometer ileld exciting winding II thanwould be obtained without this field exciting winding II.

In Fig. 2 I have shown another embodiment of my invention wherein anelectrical system is arranged to test a prime mover ll, such as annternal combustion engine, arranged to drive the rotatable member ll ofa main dynamoelectric machine arranged as a dynamometer for testing theengine. The rotatable member H is adapted to be driven bythe prime moverM by a coupling or shaft 12 and is also connecied by a suitableconnection, such as a shalt ii. to the rotatable ileld member 4! of analternaior arranged as a source of auxiliary excitation for thedynamometer exciter control system. The rotatable member I! is connectedby a suitable coupling or shait II to the rotatable member or armaturell oi an auxiliary direct current exciter provided with an armaturewinding connected to s commutator 40 having contact brushes 1 and ll.

As in the arrangement of Fig. 1, this system is adapted to provide anon-linear torque-speed characteristic to the dynamometer by providing acorresponding excitation thereto. This is obtained by the arrangementand connection of the excitation control system for the machine.Excitation is provided to the auxiliary direct current exciter by afield exciting winding II which is connected in series with a variableresisior ll arranged to control the energisstion thereoi and across asubstantially constant voltage source of direct current electrical powersup-, ply I. Since the alternator rotatable member It and the auxiliaryexciter armature ll are arranged to be driven at speeds responsive tothe speed oi the dynamometer ii. the voltage induced in the auxiliaryexciter arms-tine between the brushes l1 and l is substantially coal tothe speed oi the dynamometer ii and the engine II. A potentiometer l! isacross the source of electrical power and the auxiliary exciter armatureis connected supply ll eonnectedinserieswithsportionoi'the potentiometerbetween the terminals BI and N therethis msnnentheoiandacroslsliprlngslleonnectedtotherotatebleneldmemberltoitbesrmature.In excitation oi the alternator meybevarledtosuitthetypeprlmemoverwbichistobetutedlndthlvmoftlm auxiliary be made to'edd to the voltageelectrical power supply Ii or citing member 41 of the to the speed orthe dynamcrneter ii. The alternator is provided with an armature'winsmsltinwmchsvoitaseismduees roportional to theexcitation and speedoi the rotatable exciting member 43 and, since this excitation isproportional to the alternator speed, the voltage induced in thisarmature winding 3 substantially equal to the square of the speed 0! thealternator and, therefore. of the speed 01' the dynamometer II. Anon-linear reactor '1 is connected in series with the alternatorarmature winding It and this circuit is connected across the terminals58 and II of a full-wave rectifier. This non-linear reactor is asubstantially constant fiux device with varying frequency, such that itis for the voltage of the alternator winding I! to rise faster than thechange in speed of the alternator in ordertoobtainachangeinfiuxinthereactorora change in current through thefull-wave rectifier. This is obtainable by the non-linear voltage whichis genearated in the winding it proportionawltothesquareofthespeedoi'themac An auxiliary exciter of the type showninthis figure may not be suiliciently sensitive and may have too slow aspeed of response to provide the desired control for the maindynamometer. In order to increase these two characteristics of thesystem, the main generator or dynamometer is provided with a fieldexciting winding 28 which is arranged to be energized by a main exciter21 of the armature reaction excited typ such as an amplidyne generator.This main exciter 21 is provided with a rotatable member or armature 28and field exciting windings It and Ii corresponding to these elementsdescribed above with reference to Ffig. 1. In this arrangement, thefield exciting winding 36 is connected across the terminals 60 and ii01' the full-wave rectifier connected across the alternator armature itas a non-linear voltage source of electrical power supply. The operationof this exciter is essentially the same as that described above withreference to Fig. 1. In the arrangement illustrated, one additionalfield exciting winding I! is arranged on the exciter and is connectedacross the secondary winding CI oi. a transformer hav-' ing a primarywinding II connected across the driven by the engine ll through a shaftit and is adapted to drive a rotatable member I 0! an induction clutchthrough a suitable connection such as a shaft or a coupling .8. Thisinduction clutch is provided with a concentrically rotatably mountedelement 81 which is adapted to be excited by exciting windings it whichare energised from a suitable source 89 of direct current electricalpower supply, connected in series with a variable resistance III forcontrolling the energization or the exciting winding '8. The rotatablymounted clutch member 81 is arranged to be restrained by a resilientspring ll secured to the member 61 and to a stationary support II. Thespring H has a linear resistance displacement characteristic such thatthe rotational displacement of the clutch member I! is proportional tothe torque thereon and is. therefore. proportional to the speed of therotatable member H oi the dynamometer. A cam I3 is mounted on a shaft 14connected to the rotatably supported clutch member 61, and this cam isformed with a nonlinear cam surface corresponding to a desired operatingcharacteristic of the dynamometer II. A voltage regulator 15 isconnected to an alternating current source of electrical power supply Itand is adapted to be controlled by a cam follower II which is arrangedto engage the nonlinear cam surface of the cam ll such that thedisplacement of the cam follower 11 and, therei'ore, the output voltageof the voltage regulator 18 is responsive to the characteristicrepresented by the cam 12 and to the displacement of the clutch member81 and, therefore, to the speed of the rotatable member H oi thedynamometer.

' This response of the voltage regulator, however,

amplidyne exciter armature 2| and the exciter compensating fieldexciting winding 34. Under steady state conditions. no voltage isinduced in the secondary winding ll of the transformer, and therefore,the field exciting winding I! is normally d. Undertransient conditions.voltage is induced in the secondary winding I of the transformer and theiield exciting winding I! is energized so as to provide a component ofexcitation along the secondary brush commutating axis of the mainexciter 11 to induce a voltage between the'primary brushes 2! and 8.which is substantially equal and opposite to the transient disturbancewhich caused the energizetion. of the fleld exciting winding 8!. Thisheld exciting winding arrangement tends to stabilise the action oi theexciter 21. As in the arrange- -is a non-linear function of the speed ofthe rotatable member H as the suriada of the cam 13 corresponds to anon-linear characteristic of the dynamometer. The output terminals ofthe voltage regulator 15 are connected to terminals II and ll of afull-wave rectifier. As in the arrangement shown in Figs. 1 and 2. theoutput of the full-wave rectifier might not be sufllciently sensitiveand might have too slow a speed of response to provide the desiredcontrol of the main dynamometer. These characteristics are improved byproviding a main exciter II similar to the main exciters of the systemsshown in Figs. 1 and 2. In this construction, the dynamometer isprovided with a field exciting winding 2! energized by .the armature IIof the main exciter 21 and is controlled by a main field excitingwinding II connected to the output terminals Id and II of the full-waverectifier. This main exciter also is provided with a compensating fieldexciting winding ll, an auxiliary control field exciting winding ll anda stabilizing field exciting winding '2 connected in the same manner asthose oi the main exciter shown in Fig. 3. The operation of the mainexciter 21 is substantially the same as that described above withrespecttoll'igs. 1 and ilandprovidesamorerafld increase in theenergizing current of the dynamometer ileld exciting winding It thanwould be obtained if this field exciting winding were to be connecteddirectly to the output terminals II and ll of the full-wave rectifier.

While I have illustrated and described particular embodiments of myinvention. modifications thereof will occur to those skilled in the art.I desire it to be understood, therefore, that my invention is not to belimited to the particular arrangements and connections disclosed. and Ifications which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent 01 the UnitedStates is:

-i. An electrical system including a main dynamo-electric machine havinga field exciting winding. an exciter arranged to energize said maindynamo-electric machine field exciting winding, means including a fieldexciting winding for providing a component of excitation to saidexciter, means for providing to said exciter field exciting winding anenergizing voltage responsive to the speed of said main dynamo-electricmachine, means including a second field exciting winding for providing acomponent of excitation to said exciter along the same axis as saidexciter firstmentioned field exciting winding, and means for energizingsaid second field exciting winding only when the energizing currentsupplied by said exciter to said dynamo-electric machine field excitingwinding varies from a predetermined value relative to saidfirst-mentioned exciter field exciting winding energizing voltage.

2. An electrical system including a main dy namo-electric machine havinga field excitin winding, an exciter arranged to energize said maindynamo-electric machine field exciting winding, means including a fieldexciting winding for providing a component of excitation to saidexciter, means for providing to said exciter field exciting winding anenergizing voltage nonlinearly responsive to the speed oi said maindynamo-electric machine, means including a second field exciting windingfor providing a component of excitation to said exciter along the sameaxis as said exciter first-mentioned field exciting winding, and meansfor energizing said second field exciting winding only when theenergizing current supplied by said exciter to said dynamo-electricmachine field exciting winding varies from a predetermined valuerelative to said first-mentioned exciter field exciting windingenergizing voltage for maintaining a predetcrmined relationshiptherebetween.

3. An electrical system including a main dynamo electric machine havinga field exciting winding, an exciter arranged to energize said maindynamo-electric machine field excitin winding, means including a fieldexciting winding for providing a component 0! excitation to saidexciter, means for providing to said exciter field exciting winding anenergizing voltage dependent on a predetermined desired characteristicof said main dynamo-electric machine and responsive to, the speed ofsaid main dynamo-electric machine, means including a second fieldexciting winding for providing a component of excitation to said exciteralong the same axis as said exciter firstmentioned field excitingwinding, and means for energizing said second field exciting windingdependent on a predetermined relationship of the energizing currentsupplied by said exciter to said dynamo-electric machine field excitingwinding to said first-mentioned exciter field exciting windingenergizing voltage for maintaining a predetermined relationshiptherebetween.

4. An electrical system including a main dynamo-electrlc machine havinga field exciting winding, an exciter arranged to energize said maindynamo-electric machine field exciting' winding, means including a fieldexciting winding for providing a component oi excitation to saidexciter, means for providing to said exciter field exciting winding anenergizing voltage re-- sponsive to the speed of said maindynamo-electric machine, means including a second field exciting windingfor providing a component 0! excitation to said exciter along the sameaxis as said exciter first-mentioned field exciting winding, and meansfor energizing said second field exciting winding dependent on apredetermined relationship of the energizing current supplied by saidexciter to said dynamo-electric machine field exciting winding to saidfirst-mentioned exciter field exciting winding energizing voltage formaintaining a predetermined relationship therebetween.

5. An electrical system including a main dynamo-electric machine havinga field exciting winding, an exciter having an armature provided with awinding and a commutator connected thereto, a set of primary brushes anda set of secondary brushes electrically displaced about said commutatorfrom said primary brushes for providing a primary circuit and asecondary cir cult respectively through said armature, means forelectrically connecting together said primary brushes to complete saidprimary circuit, means for connecting said secondary brushes to saidmain dynamo-electric machine field exciting winding, means including amain field exciting winding for said exciter for providing a componentof excitation thereto along the secondary brush commutating axisthereof, voltage means responsive to the speed of said maindynamoelectric machine for energizing said exciter main field excitingwinding, and means including a second field exciting winding forproviding .a component of excitation along the secondary brushcommutating axis of said exciter responsive to a predeterminedrelationship between the secondary brush current oi said exciter andsaid main field exciting winding energizing voltage.

6. An electrical system including a main dyhomo-electric machine havinga field exciting winding, a main exciter arranged to energize said maindynamo-electric machine field exciting winding, means including a fieldexciting winding for providing a component of excitation to said mainexciter, means for providing to said main exciter field exciting windingan energizing voltage non-linearly responsive to the speed of said maindynamo-electric machine, said lastmentioned means including an auxiliaryexciter having a field exciting winding, means for energizing saidauxiliary exciter field exciting winding for inducinga component ofvoltage in said auxiliary exciter substantially dependent on the speedthereof. a second field exciting winding for said auxiliary exciter,means for energizing said second auxiliary exciter field excitingwinding, responsive to the volta e of said auxiliary exciter forinducing a non-linear voltage in said auxiliary exciter, means includinga second field exciting winding for providing a component of excitationto said main exciter along the same axis as said exciter first-mentionedfield exciting winding, and means for energizing said main excitersecond field exciting winding dependent on a predetermined relationshipof the current of said main exciter brushes to said main exciterfirst-mentioned field exciting winding en ergiz'lng voltage formaintaining a predetermined relationship therebetween.

'7. An electrical system including a main dyname-electric machine havinga field exciting winding, a main exciter arranged to energize said maindynamo-electric machine field excitinl winding, means including a fieldexciting winding for providing a component of excitation to saidexciter, means for providing to said main exciter field exciting windingan energizing voltage non-linearly responsive to the speed of said maintric machine, said last-mentioned means including an alternator and anauxiliary exciter driven at a speed responsive to the speed of said maindynamo-electric machine, means including a field exciting winding iorexciting said auxiliary exciter for inducing a volta e thereinsubstantially responsive to the speed thereof, a substantially constantvoltage source of electrical power supply, means for exciting saidalternator, means for connecting said auxiliary exciter and said sourceoi electrical power supply in series across said alternator excitingmeans for providing a non-linear excitation to said auxiliary exciter, anon-linear reactor, a full-wave rectifier, meansfor connecting saidnon-linear reactor and said full-wave rectifier in series across theoutput voltage of said alternator. means for connecting the outputterminal oi said full-wave rectifier across said main exciter fieldexciting winding, means including a second fieldexciting winding forproviding a component of excitation to said main exciter along the sameis as said main exciter first-mentioned field exciting winding, andmeans for energizing said main exciter second field exciting windingdependent on a predetermined relationship or the current oi said mainexciter secondary brushes to said main exciter first-mentioned fieldexcitins winding energizing voltage for maintaining a predeterminedrelationship therebetween.

a. An electrical system including a main lay-Q name-electric machinehaving a field exciting winding. an exciter arranged to energize saidmain dynamo-electric machi'ne field exciting winding, means including afield exciting winding for providing a component oi excitation to saidexciter, means for providing to said exciter field exciting winding anenergizing voltage nonlinearly responsive to the speed of said maindynamo-electric machine. said last-mentioned means including an inductorclutch having one element driven at a speed responsive to the speed orsaid prime mover and another element arrangedtodriveashammeansi'orresistingrctation 01' said shai't linearly responsive to rotatlonaldisplacement oi said shalt. a cam arranged trical power supply, menu foroperating said voltage regulator responsive to operation of said can,means including a second field exciting windinglor providing a componentof excitation tosaid exciteralongthesameaxisassaidexciter'first-mentioned field exciting winding, and means for energizing saidsecond field exciting winding dependent on a predetermined relationshipoi the current of said exciter secondary brushes to said first-mentionedexciter field exciting winding en. .crgising voltage ior maintaining apredetermined relationship therebctwcen.

; 9. A prime mover electrical testing system in cluding a main gemratordriven by said prime moves. a field exciting winding for said maingenerator. an exciter having an armature provided with a winding and acommutator connectedtheretmasetoiprimar bmshesandasetoi secondarybrushes electrically displaced about said commutator from said primarybrushes for cuit respectively through said armature, means forelectrically connecting together said primary brushes to complete saidprimary circuit. means for connecting said ,secondary brushes to saidmain generator field exciting winding, means including a main fieldexciting winding for said exciter for providing a, component ofexcitation thereto along the secondary brush commutating axis thereof,voltage means dependent von a predetermined desired characteristic orsaid main generator and responsive to the speedgoi said main generatorfor energizing said exciter main field exciting winding, and meansincluding a second field exciting winding for providing a component ofexcitation along the secondary brush commutating axis of said, exciterresponsive to a predetermined relationship between the energization ofsaid generator field exciting winding and the energization oi saidexciter main field exciting winding energizing voltage.

10. A prime mover electrical testing system including, a main generatordriven by said prime mover, a field exciting winding for said maingenerator. an exciter having an armature provided with a winding and acommutator connected thereto, a set of primary brushes and a set 01'secondary brushes electrically displaced about said commutatdr from saidprimary brushes ior providing a primary circuit and a secondary circuitrespectively through said ar mature, means for electrically connectingtogether said primary brushes to complete said primary circuit, meansfor connecting said secondary brushes to said main generator fieldexciting winding, means ineluding a main field exciting winding ior saidexciter for providing a component of excitation thereto along thesecondary brush commutating axis thereof, voltage means dependent on apredetermined desired characteristic oi' said main generator andresponnve to the speed of said main generator for energizing saidexciter main field exciting winding, and means including a second fieldexciting winding for providing a component of excitation along thesecondary it brush commutating axis of said exciter responsive to apredetermined relationship between the secondary brush current oi saidexciter and said exciter main field exciting winding energizing voltage.

11. A prime mover electrical testing system in- .cluding a maingenerator driven by aid prime mover, a field exciting winding for saidmain generator, on exciter having an armature provided with a windingand a commutator connected thereto, a set of primary brushes and a setoi secondary brushes electrically displaced about said commutator iromsaid primary brushes for providing a primary circuit and a secondmcanfor electrically connecting together said primary brushes to completesaid primary circuit, means for connecting said secondary brushes tosaid main generator field exciting winding, means including a main fieldexciting winding for said exciter tor providinga component of excitationthereto along the secondary brush commutating axis thereof, voltagemeans nonlinearly responsive to the speed oi said main generator forenergizing said exciter main field exciting winding, and means includinga second field exciting winding ior providing a component oi excitationalong the secondary brush commutating axis or said exciter responsive toa predetermined relationship between the secondary providing a primarycircuit and a secondary cirll brush current of said exciter and saidexciter ary circuit respectively through said armature.

main field exciting winding energizing voltage.

12. A prime mover electrical testing system including a main generatordriven by said prime mover, a field exciting winding for said maingenerator, an exciter having an annature pro I vided with a winding anda commutatorconnectedthereto,asetoiprimarybrushesanda set of secondarybrushes electrically displaced about said commutator from said primarybrushes !or providing a primary circuit and a secondary circuitrespectively through said armature, means ior electrically connectingtogether said primary brushes to complete said primary circuit, mean forconnecting said secondary brushes to said main generator field excitingwinding, means including a main field exciting winding for said exciterfor providing a component of excitation thereto along the secondarybrush commutating axis thereof, voltage means non-linearly responsive tothe speed of said main generator for energizing said exciter main iieldexciting winding, means including a second field exciting winding !orproviding a component of excitation along the secondary brushcommutating axis of said exciter. and means for energizing said secondfield exciting winding dependent on a predetermined relationship betweenthe secondary brush current of said exciter and said exciter main fieldexciting winding energizing voltage for maintaining a predeterminedrelationship therebetween.

13. A prime mover electrical testing system including a main generatordriven by said prime mover, a field exciting winding for said maingenerator, an exciter having an armature provided with a winding and acommutator conncctedtheret asetoiprimarybrushesanda set 01' secondarybrushes electricallydmplaced about said commutator from said primarybrushes for providing a primary circuit and a secondary circuitmspectively through said armature, meam for electrically connectingtogether said primary brushes to complete said primary circuit. meansfor connecting said secondary brushes to said main generator iieldexciting winding, means including a main field exciting winding ior saidexciter tor providing a component of excitation thereto along thesecondary brush commutatlng axis thereof, voltage means responsive tothe speed 01 said main generator for energizing said exciter main fieldexciting winding, means including a second held exciting winding forproviding a component oi excitation along the secondary brushcommutating axis of said exdter. and means for energiflng saidsecondiieidexcitingwindingdependentonapredetermined relationship betweenthe secondary brush current said exciter andsaid exciter main iieldexciting winding energizing voltage for maintaining a relationship Vlaaprlmemoverelectrlcaitestinggystemincludingamaingeneratordrivenbysaidprlmemovenaiield exciting winding tor said main generatonamalnexciter havinganarmature brinhesrorprovidingapflmarycircuit anda secondary circuitrsspecidvely through said armature. means for electrically connectingtogethcraaidprimarybrushestocompletesaidprlmary circuit, means forconnecting said secondarybmshestosaidnialngeneratorneldexciting winding,means including a main field exciting winding for said main exciter iorproviding a component oi excitation thereto along the secondary brushcommu'tating axis thereof, voltage means non-linearly responsive to thespeed of said main generator for energizing said main exciter main fieldexciting winding, said last-mentioned means including an auxiliaryexciter having a field exciting winding. means for energizing saidauxiliary exciter field exciting winding for inducing a component oivoltage in said auxiliary exciter substantially dependent on the speedthereof, a second field exciting winding for said auxiliary exciter,means for energizing said auxiliary exciter second field excitingwinding responsive to the voltage or said auxiliary exciter for inducinga non-linear voltage in said auxiliary exciter. and means including asecond field exciting winding (or providing a component of excitationalong the secondary commutating axis of said main exciter responsive toa predetermined relationship between the secondary brush current of saidmain exciter and said main exciter main fleld exciting winding energimngvoltage for maintaining a predetermined relationship therebetween.

15. A prime mover electrical testing system including a main generatordriven by said prime mover, a field exciting winding for said maingenerator, a main exciter having an armature provided with a winding anda commutator connected thereto, a set 0! primary brushes and a set ofsecondary brushes electrically displaced about said commutator from saidprimary brushes for providing a primary circuit and a secondary circuitrespectively through said armature, means for electrically connectingtogether said primary brushes to complete said primary circuit, meansfor connecting said secondary 40 brushes to said main generator fieldexciting winding, means including a main iield exciting winding for saidmain exciter for providing a component of excitation thereto along thesecondary brush commutating axis thereof, voltage means non-linearlyresponsive to the speed oi said main generator for energizing said mainexciter main ileld exciting winding, said last-mentioned means includingan alternator and an auxiliary exciter driven at aspeed responsive tothe speed 0! said dynamo-electric machine, means including a fieldexciting winding for exciting said auxiliary exciter for inducing avoltage therein substantially responsive to the speed thereoi, asubstantially constant voltage source of electrical power supply. meansi'or exciting said altemator. means for connecting said auxiliaryexciter and said source of electrical power-r supply in'series acrosssaid alternator exciting means tor providing a non-linear excitation insaid auxiliary exciter. a non-linear reactor, a

toll-wave rectifier, means for said non-linear reactor and saidfull-wave rectifier in series across the output voltage of saidalternator, means for ecting the output termihill of said full-waverectifier across said main exciter iield exciting winding, and meansinclud. ing a second ileld exciting winding for providing a component ofexcitation along the secondary commutating axis 0! said main exciterresponive to a predetermined relationship between the secondary brushcurrent of said main exclter' and said main exciter main iield excitingwinding energizing voltage for maintaining a predetermined relationshiptherebetween.

is. A prime mover electrical testing system in.

eluding a main generator driven by said prime mover, a field excitingwinding for said main generator, an exciter having an armature providedwith a winding and a commutator connected thereto, a set primary brushesand a set of secondary brushes electrically displaced about saidcommutator from said primary brushes for providing a primary circuit anda secondary circuit respectively through said armature, means forelectrically connecting together said primary brushes to complete saidprimary circuit, means for connecting said secondary brushes to saidmain generator field exciting winding, means including a main fieldexciting winding for said exciter for providing a component ofexcitation thereto along the secondary brush commutating axis thereof,voltage means non-linearly responsive to the speed of said maingenerator for energizing said exciter main tield exciting winding, saidlast-mentioned means including an inductor clutch having one elementdriven at a speed responsive to the speed 01' said prime mover andanother element arranged to drive a shaft, means for resisting rotationof said shaft linearly responsive to rotational displacement oi saidshalt, a cam arranged to be driven by said shaft and having a non-linearcontour representing a desired speed responsive characteristic of saidmain generator, a voltage regulator arranged to be connected to a sourceof electrical power supply, means for operating said voltage regulatorresponsive to operation of said cam, means including a second ileldexciting winding ior providing a component of excitation along thesecondary brush commutating axis of said exciter, and means forenergizing said second field exciting winding dependent on a.predetermined relationship between the secondary brush current of saidexciter and said exciter main field exciting winding energizing voltagefor maintaining a predetermined relationship therebetween.

17. A dynamo-electric machine of the armature reaction excited typeincluding a rotatable member having a winding and a commutator connectedthereto, means including a set of primary brushes and a set of secondarybrushes electrically displaced about said commutator from said primarybrushes for providing a primary and secondary circuit respectivelythrough said rotatable member winding, means for electrically connectingtogether said primary brushes tlon due to current in said rotatablemember seeondary circuit, a second ileld exciting winding arranged toprovide a component of excitation along the secondary brush commutatlngaxis of said machine, voltage means for energizing said second fieldexciting winding, a third field exciting winding arranged to provide acomponent or excitation along the secondary brush commutating axis ofsaid machine, and means for energizing said third fleld exciting windingrespong ve to variations in the current in said secondary circuit formaintaining a predetermined relationship between the current in saidsecondary circuit and the energizing voltage oi said second fieldexciting winding.

18, A dynamo-electric machine of the armature reaction excited typeincluding a rotatable member having a winding and a commutator connectedthereto. means including a set of primary brushes and a set of secondarybrushes electrically displaced about said commutator from said primarybrushes for providing a primary and a secondary circuit respectivelythrough said rotatable member winding, means for electrical- 1yconnecting together said primary brushes externaily oi said rotatablemember winding, means including it held exciting winding responsive tocurrent in said secondary circuit for providlng a component 01excitation equal and opposits to the component of excitation due tocurrent in said rotatable member secondary circult. a second fieldexciting winding arranged to provide a component of excitation along thesecondai'y brush commutating axis or said machine, variable voltagemeans for energizing said second field exciting winding, a third iieldexciting winding arranged to provide a component of excitation along thesecondary brush commutating axis of said machine, and means forenergizing said third field exciting winding dependent uponthe-diiierences in potential between the energizing voltage of saidsecond iield exciting winding and a voltage responsive to the current insaid secondary circuit.

mm A. EDWARDS.

